Optically black waters in the northern Baltic Sea

Abstract

[1] The peculiar bio-optical properties of the northernmost waters of the Baltic Sea (Bothnian Sea and Bothnian Bay) are illustrated by exploiting unique in situ measurements of apparent and inherent optical properties collected in 2007. Specifically, this study shows that the high values of absorption by colored dissolved organic matter (a ys (412) around 1.4 m −1 ) resulting from the presence of humic matter brought by the numerous Swedish and Finnish rivers alimenting the basin are not correlated with high concentrations of particles as generally observed in the southern Baltic Sea. As a consequence, extremely low values (i.e., less than 0.5) of the ratio of scattering to absorption are observed in the blue spectral region. The corresponding spectra of normalized water leaving radiance are close to satisfy the "black pixel" assumption in the blue and even in the green part of the visible spectrum. Consequently, the Bothnian Sea and most of all the Bothnian Bay, appear ideal candidates for studies on atmospheric corrections and vicarious calibration of ocean color sensors in coastal waters.

The OLCI Neural Network Swarm (ONNS): A Bio-Geo-Optical Algorithm for Open Ocean and Coastal Waters

“…Conclusions on the performance using OLCI Earth observation data can be drawn after throughout validation against field measurements or other bio-geo-optical algorithms. The shown example demonstrates that ONNSestimated ocean color products are mostly within the range of observed concentrations (e.g., Kowalczuk, 1999;Berthon and Zibordi, 2010;Pitarch et al, 2016;Ylöstalo et al, 2016). From our present point of view, we conclude that the new ONNS inwater algorithm is suited for the remote sensing estimation of water properties and constituents of most natural waters.…”

“…The concentration ranges, however, fit to observations by Berthon and Zibordi (2010). The regional distribution of CDOM, including the east-west gradient and high concentrations in the northern Baltic and Gulf of Finland, is plausible (e.g., Kowalczuk, 1999;Berthon and Zibordi, 2010;Ylöstalo et al, 2016). The corresponding uncertainty maps partly mirror the boundaries of the dominant water classes.…”

Chromophoric dissolved organic matter of black waters in a highly eutrophic Chinese lake: Freshly produced from algal scums?

“…Although black water events have been reported in several water bodies worldwide [13,14,[32][33][34], the source of CDOM in black water spots remains largely unknown. Unraveling the source of CDOM in black water blooms could be of important advisory value to local lake water resource managers.…”

Temporal and spatial changes of macrobenthos community in the regions frequently occurring black water aggregation in Lake Taihu

“…It poses severe threats to the drinking water safety. With the aggravation of cyanobacteria bloom, black water aggregation has occurred frequently in many inland lakes and continental seas, such as Florida Keys in USA 24 , East China sea 25 and Baltic in Europe 26 . The black water aggregation in Lake Taihu mostly occurs in areas with high levels of polluted sludge and accumulated cyanobacteria 27,28 .…”